1. Field of the Invention
This application is a continuation-in-part of the inventor's U.S. Ser. No. 12/650,347, filed on Dec. 30, 2009, which is a continuation in part of the inventor's U.S. Ser. No. 12/626,890, Nov. 28, 2009. As such, it relates to method and apparatus for determining fluid flow rates by measuring the transit times of acoustic pulses transmitted through a flowing fluid.
2. Background Information
The accuracy of a transit-time flow measurement can be limited by the accuracy with which the speed of sound of the flowing fluid is known when that speed is used to determine the spacing between the rate measuring transducers. Moreover, a further accuracy limitation is imposed by the accuracy with which the inside diameter of the pipe is known.
In Ser. No. 12/650,347 the inventor describes transit time arrangements for measuring both the speed of sound of the fluid and the internal diameter of the pipe.
In U.S. Pat. No. 6,973,842 the inventor describes an acoustic transit time probe in which one or more transducers on a probe are used for measuring pipe diameter.
In U.S. Pat. No. 6,584,860 Feldman et al. teach approaches to determining the depth to which a probe is inserted into a pipe. In one of these approaches a first portion of an acoustic beam is incident on a reflector portion of a flow measurement path and a second portion of the beam reflects off an internal wall of the pipe to determine insertion depth.